Computing devices, such as notebook computers, personal data assistants (PDAs), kiosks, and mobile handsets, have user interface devices, which are also known as human interface devices (HID). One user interface device that has become more common is a touch-sensor pad (also commonly referred to as a touchpad). A basic notebook computer touch-sensor pad emulates the function of a personal computer (PC) mouse. A touch-sensor pad is typically embedded into a PC notebook for built-in portability. A touch-sensor pad replicates mouse x/y movement by using two defined axes which contain a collection of sensor elements that detect the position of a conductive object, such as a finger. Mouse right/left button clicks can be replicated by two mechanical buttons, located in the vicinity of the touchpad, or by tapping commands on the touch-sensor pad itself. The touch-sensor pad provides a user interface device for performing such functions as positioning a pointer, or selecting an item on a display. These touch-sensor pads may include multi-dimensional sensor arrays for detecting movement in multiple axes. The sensor array may include a one-dimensional sensor array, detecting movement in one axis. The sensor array may also be two dimensional, detecting movements in two axes.
One type of touchpad operates by way of capacitance sensing utilizing capacitive sensors. The capacitance detected by a capacitive sensor changes as a function of the proximity of a conductive object to the sensor. The conductive object can be, for example, a stylus or a user's finger. In a touch-sensor device, a change in capacitance detected by each sensor in the X and Y dimensions of the sensor array due to the proximity or movement of a conductive object can be measured by a variety of methods. Regardless of the method, usually an electrical signal representative of the capacitance detected by each capacitive sensor is processed by a processing device, which in turn produces electrical or optical signals representative of the position of the conductive object in relation to the touch-sensor pad in the X and Y dimensions. A touch-sensor strip, slider, or button operates on the same capacitance-sensing principle.
Another user interface device that has become more common is a touch screen. Touch screens, also known as touchscreens, touch panels, or touchscreen panels are display overlays which are typically either pressure-sensitive (resistive), electrically-sensitive (capacitive), acoustically-sensitive (SAW—surface acoustic wave) or photo-sensitive (infra-red). The effect of such overlays allows a display to be used as an input device, removing the keyboard and/or the mouse as the primary input device for interacting with the display's content. Such displays can be attached to computers or, as terminals, to networks. There are a number of types of touch screen technologies, such as optical imaging, resistive, surface acoustical wave, capacitive, infrared, dispersive signal, piezoelectric, and strain gauge technologies. Touch screens have become familiar in retail settings, on point of sale systems, on ATMs, on mobile handsets, on kiosks, on game consoles, and on PDAs where a stylus is sometimes used to manipulate the graphical user interface (GUI) and to enter data.
FIG. 1A illustrates a conventional touch-sensor pad. The touch-sensor pad 100 includes a sensing surface 101 on which a conductive object may be used to position a pointer in the x- and y-axes, using either relative or absolute positioning, or to select an item on a display. Touch-sensor pad 100 may also include two buttons, left and right buttons 102 and 103, respectively, shown here as an example. These buttons are typically mechanical buttons, and operate much like a left and right buttons on a mouse. These buttons permit a user to select items on a display or send other commands to the computing device.
FIG. 1B illustrates a conventional linear touch-sensor slider. The linear touch-sensor slider 110 includes a surface area 111 on which a conductive object may be used to control a setting on a device, such as volume or brightness. Alternatively, the linear touch-sensor slider 110 may be used for scrolling functions. The construct of touch-sensor slider 110 may be the same as that of touch-sensor pad 100. Touch-sensor slider 110 may include a sensor array capable of detection in only one dimension (referred to herein as one-dimensional sensor array). The slider structure may include one or more sensor elements that may be conductive traces. By positioning or manipulating a conductive object in contact or in proximity to a particular portion of the slider structure, the capacitance between each conductive trace and ground varies and can be detected. The capacitance variation may be sent as a signal on the conductive trace to a processing device. It should also be noted that the sensing may be performed in a differential fashion, obviating the need for a ground reference. For example, by detecting the relative capacitance of each sensor element, the position and/or motion (if any) of the external conductive object can be determined. In one embodiment, it can be determined which sensor element has detected the presence of the conductive object, and it can also be determined the motion and/or the position of the conductive object over multiple sensor elements.
One difference between touch-sensor sliders and touch-sensor pads may be how the signals are processed after detecting the conductive objects. Another difference is that the touch-sensor slider is not necessarily used to convey absolute positional information of a conducting object (e.g., to emulate a mouse in controlling pointer positioning on a display), but rather relative positional information. However, the touch-sensor slider and touch-sensor pad may be configured to support either relative or absolute coordinates, and/or to support one or more touch-sensor button functions of the sensing device.
FIG. 1C illustrates a conventional sensing device having three touch-sensor buttons. Conventional sensing device 120 includes button 121, button 122, and button 123. These buttons may be capacitive touch-sensor buttons. These three buttons may be used for user input using a conductive object, such as a finger.
In the design and implementation of many hand-held devices, cellular phones for example, the user is required to manipulate a number of push-buttons or switches for the purpose of dialing, storing information, accessing information, menus, etc. In many cases, this activation is done in non-pristine environments where direct visual monitoring of the display(s) in these devices is not possible. In these cases, the user requires some level of feedback from the device to indicate proper application of a switch closure or button press. Also, when a device of this type is operated where the user has no direct visual access to the button or sensor array, or where the user is physically handicapped such that visual confirmation is not possible, the user requires some type of tactile mechanism, such as a surface feature, from the device to provide a reference location in the sensor array. Such feedback may be static or dynamic in nature.
In one conventional design, as described in U.S. Pat. No. 6,704,005, passive mechanical tactile feedback is provided to the user by mechanical devices under the switch or button array. These mechanical elements may serve no other purpose in the operation of the button or switch. Also, since these mechanical devices are activated only after the switch or button is pressed, they serve no function for the location of any specific switch within the switch or button array.
The primary disadvantage of the conventional design, described above, is one of cost. Adding these mechanical elements increases the unit cost of the product. They also create a potential point of failure in the device, such that the normal button press or switch activation may still operate correctly, but the overall product would no longer meet specifications due to the failure of the passive mechanical, tactile feedback from one or more of the buttons. They may also incorrectly indicate activation or acceptance of a button press, even if the power source for the unit is removed, discharged, or otherwise disabled. These additional mechanical feedback elements would also increase the weight of the overall product, which is considered important in portable devices. Their inclusion in the button array also potentially increases the thickness of the array, which is also not considered to be beneficial to the use or marketability of the device.
The converse of invalid response also exists, in that the normal electrical detection mechanism, due to contact contamination, for example, may not report a button press to the device, while the passive mechanical feedback may indicate activation.
FIGS. 1D and 1E illustrate conventional mechanical keys of a portion of a keyboard and a keypad. In conventional designs of keyboards (e.g., keyboard 130) and keypads (e.g., keypad 140), such as those found on a desktop or laptop computer, passive tactile feedback for user detection of a reference location may be provided by including surface features (e.g., 135 and 136 of FIG. 1D and 144 of FIG. 1E), such as bumps or ridges, in the material (e.g., plastic) used to make the keys on the keyboard. These surface features may be located on the ‘F’ and ‘J’ keys 131 and 134 in standard QWERTY keyboards 130 and the ‘5’ key 142 of keypad 140. The keys 131, 134, and 140 indicate the default or ‘home’ location (e.g., reference location) of a user's hands for touch-typing or numeric entry applications respectively. These keys are also known as home keys or reference keys.
A similar indicator is often provided on hand-held devices, such as a mobile handset, where the keypad is significantly smaller in size. Here the sensor array is normally that of a dialing pad, a portion of which being of equivalent function as that of the standard switch matrix found on touch-tone or similar telephones. In these button or sensor arrays, the ‘home’ position (e.g., reference location) is normally that of the ‘5’ key which is located in approximately the center of the button or sensor array. To allow similar user detection of this ‘home’ reference location, the mechanical elements used to make the sensor array often contain similar molded or embossed physical features on or around the ‘5’ key.
Using mechanical feedback mechanisms, such as the mechanical device described in U.S. Pat. No. 6,704,005, or surface features (e.g., bumps or ridges 135, 136, or 144) on the keys, works well for electromechanical switches in buttons or sensor arrays, however, such electromechanical switches have many known shortcomings: they are prone to failure due to fatigue and contamination, they physically increase the weight and spatial volume of the device, and they increase the manufacturing cost of the device relative to non-mechanical forms of sensor arrays.
These handheld devices are now becoming available with touch-sensor pad surfaces used to implement dialing keypads or other forms of data entry. For aesthetic and manufacturability reasons, these touch surfaces are often implemented without surface features to indicate the ‘home’ location. In these applications, some other form of feedback must be provided to the user to allow accurate determination of the ‘home’ reference location, individual button locations, and proper-activation position of button or switch-equivalent functions.
Another conventional design is disclosed in U.S. Pat. No. 6,262,717. This application discloses the patterning of the touch responsive surface with one or more different physical patterns such that a finger, sliding across the patterns, can distinguish one area from other areas having either different patterns or no patterns present on the touch responsive surface. Unless these surface patterns are significantly large in size, a finger inside a glove will not be able to sense their presence. This design also is disadvantageous for the increase in cost per unit for adding these mechanical elements. The mechanical elements also create a potential point of failure in the device, such that the normal button press or switch activation may still operate correctly (having no moving parts) but the overall product would no longer meet specifications due to the failure of the passive tactile feedback from one or more of the buttons through wear or other external forces. Their inclusion in the button array also potentially increases the thickness of the array.
As for a patterned surface, such patterning affects the aesthetics of the product, and also provides locations where various forms of dirt and surface contaminants can become trapped, skewing the normal touch response function of the product.
While such feedback is simple to implement in mechanical switches, this is not the case where the button is electronic in nature and has no moving parts, such as in capacitive sensing sensor elements.